================================== DOCUMENT 3: SESSION 6 (S6) ================================== POLLUTION ABATEMENT (21CHO105T) Unit 1 - Session 6 I. MULTIPLE CHOICE QUESTIONS (MCQs) 1. Nitric acid in acid rain is formed from ● Answer: B) Nitrogen oxides ● Explanation: Nitrogen oxides ( , such as ) react with atmospheric moisture 𝑁𝑂 𝑥 𝑁𝑂 2 and oxygen to form nitric acid ( ). 𝐻𝑁𝑂 3 2. Acid rain causes damage to monuments mainly due to ● Answer: B) Chemical reaction with stone materials ● Explanation: Sulfuric acid in acid rain chemically reacts with calcium carbonate ( ) in marble and limestone to form soluble calcium sulfate ( ), a 𝐶𝑎𝐶𝑂 3 𝐶𝑎𝑆𝑂 4 process called "stone cancer." 3. Freshwater organisms are affected by acid rain because of ● Answer: C) Changes in water pH ● Explanation: Acid rain lowers the pH of lakes and rivers below critical survival limits (often ), leaching toxic aluminum ions ( ) into the water and 𝑝𝐻 < 5 𝐴𝑙 3+ disrupting aquatic life. 4. Pollution prevention is preferred over pollution control because it ● Answer: C) Reduces environmental damage ● Explanation: Pollution prevention eliminates pollutants directly at the source, preventing environmental damage and saving long-term waste treatment and disposal costs. 5. Environmental regulations encourage industries to adopt ● Answer: B) Cleaner and efficient technologies ● Explanation: Regulatory compliance mandates lower emissions thresholds, motivating industries to transition toward resource-efficient, low-emission technologies. II. SHORT ANSWER QUESTIONS Q1. How is acid rain formed? ● Answer: ○ Emissions: Industrial power plants and vehicles emit gaseous precursors—sulfur dioxide ( ) and nitrogen oxides ( ). 𝑆𝑂 2 𝑁𝑂 𝑥 ○ Oxidation & Hydration: These gases react with atmospheric oxygen, water vapor, and oxidants: ■ (Sulfuric acid) 𝑆𝑂 2 + [𝑂] + 𝐻 2 𝑂 → 𝐻 2 𝑆𝑂 4 ■ (Nitric acid) 2𝑁𝑂 2 + [𝑂] + 𝐻 2 𝑂 → 2𝐻𝑁𝑂 3 ○ Precipitation: These acids dissolve into cloud droplets and fall to Earth as wet deposition (rain, snow, fog) with a 𝑝𝐻 < 5. 6 Q2. What is the main aim of environmental policies? ● Answer: ○ To protect natural ecosystems, biodiversity, and human health from environmental degradation. ○ To enforce industrial compliance with pollutant discharge limits. ○ To promote sustainable development through pollution prevention, resource conservation, and adoption of cleaner production technologies. III. LONG ANSWER QUESTION 1. Acid rain is a form of precipitation that contains acidic components such as sulfuric acid and nitric acid. [Discuss the causes, chemical mechanisms, environmental impacts, and control strategies for acid rain.] ● Answer: 1. Atmospheric Chemical Reactions Acid rain forms when primary pollutants ( and ) undergo atmospheric 𝑆𝑂 2 𝑁𝑂 𝑥 transformation: ● Sulfuric Acid Formation: ● 𝑆𝑂 2 + 𝑂𝐻 • → 𝐻𝑆𝑂 3 • ● ● 𝐻𝑆𝑂 3 • + 𝑂 2 → 𝐻𝑂 2 • + 𝑆𝑂 3 ● ● 𝑆𝑂 3 + 𝐻 2 𝑂 → 𝐻 2 𝑆𝑂 4 ● Nitric Acid Formation: ● 𝑁𝑂 2 + 𝑂𝐻 • → 𝐻𝑁𝑂 3 2. Environmental and Material Impacts ● Aquatic Ecosystems: Lowering water bodies' pH below 5.0 causes acidification, triggering fish egg mortality and leaching toxic aluminum ions ( ) into stream 𝐴𝑙 3+ systems. ● Terrestrial Ecosystems & Forestry: Foliar leaching strips essential plant nutrients ( ) from leaves and soils, stunting forest growth. 𝐶𝑎 2+ , 𝑀𝑔 2+ ● Built Environment & Cultural Heritage: Acid rain degrades historical structures made of limestone and marble ( ): 𝐶𝑎𝐶𝑂 3 ● 𝐶𝑎𝐶𝑂 3 + 𝐻 2 𝑆𝑂 4 → 𝐶𝑎𝑆𝑂 4 + 𝐶𝑂 2 + 𝐻 2 𝑂 3. Abatement and Control Strategies ● Flue Gas Desulfurization (FGD): Installing industrial wet/dry limestone scrubbers to strip up to 95% of from industrial flue gases. 𝑆𝑂 2 ● Selective Catalytic Reduction (SCR): Employing ammonia-based catalytic converters to reduce exhaust to inert nitrogen gas ( ). 𝑁𝑂 𝑥 𝑁 2 ● Fuel Clean-up: Utilizing ultra-low-sulfur diesel (ULSD) and hydrodesulfurized coal feedstocks.